Dumb Question

[Seke69]

I only say dumb because I did something about a week ago, and now I can't do it again...WTF?

I need to take the gauge cluster off, to put the one I pulled out the junkyard, in. I JUST took one off, not even a week ago.... on to the question.
the wiper knob comes off with a kind of tensioning screw, how does the light knob come off? I tried a pliers around the shaft to hold it while I gave the knob a turn, but that didn't feel 'right'... I seem to remember the triangular rod being threaded... ugh. help. it's the only knob I have left, because I dropped the one from the junkyard in the mud (along with a million other knobs, screws, and fancy chrome stuff), the junkyard one came off a little too easily if I remember (maybe it was broken?). I don't want to mess this one up.

thanks in advance...